1. Field of the Invention
The present invention relates to a spectroscopic apparatus for extremely faint light emission, and more particularly, to a spectroscopic apparatus which enables spectroscopic detection of extremely faint light emission observed in the living-body specimen or the like as bioluminescence, chemiluminescence, and fluorescence from a living-body specimen.
2. Description of the Prior Art
For spectroscopic detection of extreme faint light emission such as bioluminescence, a spectroscopic method using color glass filters has been heretofore used. FIG. 7 is a block diagram for such an apparatus. Various specimens which generate extreme faint emission are received in a specimen cell or a container 21 which is controlled by a temperature regulator 22 to a predetermined temperature suitable for the measuring conditions. The emission from a light source is converged on a photoelectric surface of a photo multiplier (PM) using a tubular reflecting mirror of an ellipsoid of revolution 23. Color glass filters 25 used for spectrum analysis are arranged on a mechanically rotatable disk 26, and are successively inserted into and exchanged automatically in a measuring light path in front of the PM 24 by means of a filter drive and control device 27. The intensity of the transmitted light, after having been passed through a filter 25, is counted by the PM 24. The PM 24 used for measurement is cooled by a thermoelectric temperature control unit 28 in order to suppress heat noise pulses. Signals from the PM 24 are counted by an addition and subtraction counter 34 via a pulse amplifier 30 and a pulse height discriminator 31. A chopper 32 and a phase shifter 33 are provided to periodically intermittently feed incident light from the light source and effect digital lock-in detection. The results counted by the addition and subtraction counter 34 are recorded in a digital printer 35. Data processing, required for directly obtaining a spectral distribution, is carried out in a mini-computer 36. The results are displayed on an oscilloscope 37 and an X-Y recorder 38. In FIG. 7, reference numeral 29 designates a stabilized high voltage power source, and 39 designates a preset timer.
The spectroscopic method using color glass filters as described above is superior to a diffraction grating spectroscope in terms of brightness because light from the specimen is wholly detected. However, plural color glass filters are needed and therefore a disadvantage is that observation time becomes very long.
On the other hand, a spectroscope using a diffraction grating has a large F number which determines brightness. However, it is difficult to use the diffraction grating to detect a faint emission.
Recently, Fourier spectroscopy using a diode array is being used in various fields. This method is used where light for spectrum is relatively strong. It was impossible to use Fourier spectroscopy for spectrum analysis of an extremely faint emitted by a living specimen or the like due to the high noise of the diode.
Separate from the spectrum analysis of the extremely faint emission as described above, a two-dimensional photon counter which will be described later has been known as an apparatus for obtaining an image of a body emitting extremely faint light. However, this apparatus is merely used with a conventional spectroscope using a diffraction grating. No attempt has been made to use this apparatus with a bright spectroscope which can be used for spectroscopy of the extremely faint emission.